Demands for increased accuracy in the timing of sports events has resulted in the development of many relatively sophisticated systems for measuring an elapsed interval between initiating and terminating time points. Of course, the accuracy of any resulting measurement is firmly dependent on the ability of the system to initiate and terminate the time count at precise instants corresponding to the start and completion times of, for example, a foot race, or a skiing event, or a swim meet competition or the like. It has accordingly been commonplace for organized and officially sponsored sporting events to adopt a specific system dependent upon signal generating apparatus appropriate to the particular event or sport. In swimming and other racing sports, the automatic event time initiation signal is typically a strobe lamp flashed concurrently with the starting beeper or horn; in some cases, such a strobe may also be automatically flashed when the first swimmer to finish contacts a conventional touch plate often provided in the pool to detect such contact.
Many spectators at swim meets--and at other sporting events--have long recognized that their enjoyment in observing the races is enhanced when they themselves individually time the participants on hand-held stopwatches. A spectator may in this manner feel more like a part of the event; in addition, the use of one's own stopwatch presents an onlooker with the opportunity to obtain an elapsed time reading for a friend or relative or other particular participant irrespective of whether that individual eventually wins or places and thus receives an "official" time for the race. It is in fact a common practice at swim meets for the event officials to provide spectators with two strobe light flashes--a predetermined time interval agent--so that onlookers can verify the accuracy of their individual timing devices prior to the start of the races.
One drawback of a hand-held stopwatch--be it a standard mechanical timer or one of the readily available electronic counting and display types--is its dependence for accuracy in interval measurement on the mechanical coordination and reflexes of the user. Unless the user presses the start button or switch to initiate the measurement period at the precise moment that the race begins, the final elapsed interval measured will only approximate the actual event time. Although most users of hand-held stopwatches are cognizant that an inaccuracy of unknown magnitude physiological response time is present in the resulting measurement, few truly appreciate how great the inaccuracy can be.